High-frequency magnetrons



June 1947- R. J. BONDLEY HIGH FREQUENCY MAGNETRON.

Filed Feb. 2, 1943 Ihventor Ralph J. Bondleg,

Fig.5.

bu His Attorney.

Patented June 17, 1947 Ralph J. Bondley,

Scotia, N. Y., assignor to Gen- *eral Electric Company, a corporation ofNew ork Application February 2, 1943, Serial No. 474,426

4 Claims. (01. 250-275) My invention relates to high frequency electricdischarge devices and more particularly to ultra high frequencymagnetrons of the space resonant type. My invention is in the nature ofan improvement over the tuning arrangement described and claimed incopending application Serial No. 465,439, of Kenneth C. De Walt, filedNovember 13, 1942, and this invention.

Heretofore in the design and construction of ultra high frequencymagnetrons, difiiculty has been encountered in the provision of suitabletuning means therefor. One of the disadvantages of the prior art tuningarrangements for ultra high frequency magnetrons has been thenonlinearity and the extreme sensitiveness of the frequency controllingmeans with respect to the operating frequency of the device. Stated inother words, the prior art magnetrons of the tunable type have beendiflicult to control or ad- Just by virtue of the fact that the tuningmeans have caused within certain regions of operation an excessivechange in frequency, and within still other ranges of operation orfrequency control have entailed very slight changes in frequency uponoperation of the automatic or manual frequency controlling means.

In accordance with the teachings of my invention described hereinafter,I provide new and improved frequency controlling means for magnetronswhich obviate the above described disadvantages of the prior artarrangements.

- It is an object of my invention to provide new and improved ultra highfrequency magnetrons.

It is another object of my invention to provide new and improved ultrahigh frequency magnetrons of the space resonant type.

- It is a further object of my invention to provide new and improvedultra high frequency magnetrons-of tunable character wherein a linearrelationship is obtained between the operating frequency of themagnetron and the frequency controlling means or tuning means.

It is a still further object of my invention to provide new and improvedfrequency controlling structure for space resonant magnetrons.

Briefly stated, in the illustrated embodiments of my invention, Iprovide new and improved tuning means or frequency controlling means forultra high frequency magnetrons of the space resonant type wherein apositionable member or members are associated with the anode structuredefining the space resonant cavities, and wherein a linear relationshipis obtained between the opcrating frequency of the magnetron and thepoassigned to the assignee of effect the desired tuning operation.

space resonant sition of the tuning member or members. In the particularform of magnetron with respect to which my invention is described, Iprovide tun ing members which may be either of conductive material or ofdielectric material and which extend into openings in the anodestructure to The tuning members are inserted in the anode structure inpositions or openings within which the ultra high frequency electric andmagnetic fields of the various space resonant cavities are present orassociated.

In one embodiment of my invention a conductive or metallic annular ringextends into an annular recess in one face of the anode structure, andthe position of the ring within the structure determines the naturalfrequency of the space resonant cavities and consequently determines theoperating frequency of the device.

In another modification of my invention, the tuning means comprises aplurality of dielectric tuning stubs or cavities and thereby control thenatural frequency of the cavities and the operating frequency of thedevice.

7 For a better understanding of my invention, reference may be had tothe following description taken in connection with the accompanyingdrawing, and its scope will be pointed out in the appended claims. Fig.1 diagrammatically illustrates an embodiment of my invention as appliedto an ultra high frequency magnetron wherein the magnetic excitationtherefor is provided by a pair of longitudinally spaced permanentlymagnetized pole pieces, and Fig. 2 represents a cross sectional view ofthe anode structure including the coupling means provided for the spaceresonant cavities. Fig. 3 represents a further embodiment of myinvention wherein the tuning means comprises a plurality of dielectrictuning members which extend into the space resonant regions and aresupported by a ring construction, the details of which are shown inFigs. 4 and 5.

Referring now to Fig. 1 of the accompanying drawing, Ihave thereillustrated my invention as applied to an ultra high frequency magnetronof the space resonant type. certain general features of which arebroadly disclosed and claimed in copending patent application, SerialNo. 447,903 of Elmer D. McArthur, filed June 22, 1942, and which isassigned to the assignee of the present application.

The magnetron shown in Fig. 1 comprises a lateral wall structureprovided by a single metal tube I consisting of ferromagnetic materialsuch members which extend into the ically sealed to the or electrodesections of the container are closed by flanged members weldedorotherwise hermetinner surface of tube I. -Within the container andapproximately at its central portion there is provided an anodestructure 4 which is shown in plan view in Fig. 2*. The anode structure4 is preferably constructed 2 and 3 which are of a conductivenon-magnetic material; such as copper, and is provided with an enlargedcentral opening which surrounds a cathode structure to and whichcomprises an conductor-01a concentric transmission line 23 comprising aninner conductor 2i and an outer tubular conductor 22.

As stated above, the anode structure 4 preferably consists of copper andis supported, as

' shown in Fig. 1, by being brazed to the inner wall be describedpresently. Circumferentiall'y arranged or positioned 5 there is provideda number of space resonant regions or cavities which may take the'formof cylindrical openings 6-l3, inclusive, each of which is incommunication with the enlarged central opening 5 through a radiallyextending slot 14. Slots l4 define therebetween a plurality of electrodeor anode sections.

In order to receive a tuning member, I provide in one surface, that isthe bottom surface, of anode structure 4 an annular channel or groovel5. member or ring l6, preferably constructed of non-magnetic materialsuch as copper or silver, and which proj ects into groove l5 and is inspaced relation with respect to the walls thereof. Groove l5 may belocated at a number ofv positions with respect to openings 6-l3 andtheir associated slots l4, and the relative positions illustrated inFig. 2 are merely exemplary of one way in which these elements of theanode structure may be arranged. I have found that effective tuning orcontrol of the operating frequency is obtained by locating the annulargroove l5 within the vicinity of the junctures of cylindrical openings6-I3 and the slots I4.

As a means for coupling the various space resonant cavities defined byopenings 6-I3 and .the associated slots I4, I provide a plurality of coupling conductors l1 and II! which may be arranged in accordance with thepatterns disclosed and claimed in my copending application, Serial No.462,123, filed October 15, 1942, and which is assigned to the assigneeof the present application.

Referring more particularly to the coupling conductors l1 and I8, theseconductors are preferably arranged so that alternate metallic partsbetween slots M are electriaround the central opening of tube I. 'Arelatively large circumferential channel 23 in the anode'structureserves to reduce the overall weight.

Within the enlarged central opening 5 of the anode structure 4 there isprovided a cathode of the indirectly heated thermionic type a sleeve 24having on the outside surface thereof a suitable electron emissivematerial such as barium oxide. Within the cathode sleeve 24 there isprovided a cathode heating element 25, the upper terminal of which isconnected to an inner conductor of a concentric line to be describedpresently, and the lower terminal of which is electrically connected tothe sleeve 24.

Forthe purpose of providing a magnetic field to permit the apparatus toof sumcient intensity function in its intended manner, there is providedwithin the tube la pair of magnetic pole pieces 26 and 21 which maybepermanently magnetized and which, of course, respectively provide northand south poles, or vice versa'.

Where the magnetic pole pieces 26 and 21 are permanently magnetized,these members should be constructed of a magnetizable material having ahigh coercive force and a high energy factor. One of the materials whichmay be used in this connection is that known as Alnico meaning aparticular class of alloys of aluminum, nickel and cobalt.

In order to obtain a low reluctance connection between the bases of thepole pieces 26 and 21, 1 these pole pieces may be respectively seatedupon relatively thick disk-like members 28 and.29 consisting offerromagnetic material such as steel. For the purpose of securing thepole pieces rigidly onflxedly to these base members, use may be made ofclamping rings'3il and 3l which are slipped over the pole pieces and;welded to the members 28 and 29.

cally connected; that is, conductors i'l may be I considered asconnecting alternate electrode sections and conductors l8 may beconsidered as connecting the intervening or intermediate electrodesections. This type of connection is obtained by constructing conductorsi1 and iii .to span and to be physically separated from alternateelectrode sections. For example, one conductor ll spans the electrodesection between-m 'slots i4 associated with cylindrical openings 6 andl, and the adjacent conductor l8 spans the associated with cylindricaltends into one of the cavities, such as opening 8,

Accuratespaeing of pole pieces 26 and 21 with respect to the anodestructure 4 may be obtained by the useof. spacing rings 32 and 33 whichen-' gage the upper and bottom surfaces of the anode structure 4, andare in engagement with apertured disks 34 and 35 abutting appropriatelygolrmed shoulders on magnetic pole pieces 26 and Magnetic pole pieces 26and Time provided with longitudinally extending channels 36, and 31,respectively, the former of which is employed to receive structure forsupporting the cathode in spaced relation with respect to' anodestructure 4 and fo r supplying cathode heating current thereto. Forexample, one type of construction which may be employed for this purposeis'that disclosed and claimed in my copending patent application, SerialNo. 465,424,"flled' November 13,

1942, and which is assigned to the assignee of the present'application.This supporting structure may comprise a concentric transmission lineincluding an outer conductor 38 and an inner conductor 39, the former ofwhich is electrically connected to a supporting collar 40 which engagesthe cathode sleeve 24 and the latter of which is connected to the upperterminal of the cathode heating element 25, extending through the collar40 and insulated therefrom by means of a vitreous "insulator 4|.Conductor 39 may extend through extension of an inner comprising thecylinder 24 and serve as a support for a shielding disk 42 which is inspaced relation with the pole face of pole piece 21 and the bottomsurface of the anode structure.

The inner conductor 39 and the outer conductor 38 may be maintained inspaced relation with each other by means of a plurality oflongitudinally spaced insulators 43. The entire concentric linearrangement may be supported in a desired central position in channel36, and maintained in the proper longitudinal alinement by means of aninsulatofr u which closely engages the inner surface 9 channel 36 andthe outer surface of tubular conductor 38.

At the upper end of channel 36, the conductors 38 and 39 are connectedto externally accessible terminals 45 and 46, the latter of which arehermetically sealed by means of a suitable vitreous seal 41 which, inturn, is sealed to a flanged collar 48 welded to the upper surface ofmember 2.

The position of the ring tuning member 16 previously described inconnection with Fig. 2 is more fully appreciated by referring to thelongitudinal cross sectional view of, Fig. 1 wherein it is seen that themember or ring [6 extends into the recess .or annular groove l providedin the anode structure 4. Tuning ring I6 is provided with a flanged partl6a. Magnetic pole piece 21 is provided in its pole face with atransverse slot 49 adapted to receive and permit ready movement thereinof a transverse supporting rod 50 which is attached to flange l6a of thetuning ring l6.

Control of the position of the transverse rod 50 and hence thelongitudinal position of the tuning ring I6 is obtained by means of alongitudinal actuating rod 5| which is located in channel 31 and whichis provided with an externally accessible actuating means such as athumb-nut 52. The actuating means for the tuning structure may include acalibration scale (not shown) for indicating the position of the tuningring l6 or for indicating the operating frequency of the deviceestablished by the position of that ring. Adjusting means for rod 5|includes an hermetic seal which may comprise a deformable metallicbellows 53 which is not only sealed to the lower surface of end member 3but is also sealed to rod 5|. A metallic cap 54 surrounds the sealingbellows 53 and serves as a support for the lower extremity of rod 5|,and as a means for exerting variable pressures against the end ofbellows 53 through rod 5 I and washer 53'.

The coupling conductors I! and I8 may be arranged to lie within a recess55 provided in the bottom surface of the anode structure 4 as shown inFig. 1. If desired, a similar system or array of coupling elements maybe positioned in a recess 56 in the top surface of the anode structure4.

In the operation of an electric discharge device of the above describednature, it may be considered that the energization or excitation of thevarious space resonant cavities comprising the cylindrical openings 6-l3and the associated slots I4 is obtained by utilization of the motion ofthe electrons constituting the space charge which is effected orestablished between the outer surface of cathode sleeve 24 and thesurfaces of the electrode sections between the slots l4. By virtue ofthe application of a unidirectional potential between the anodestructure and the cathode, and the magnetic field which is provided bypole pieces 26 and 21, the electrons constituting the space charge willbe given a helical or spiral motion undergoing oscillations or gyrationsto excite the various space resonant cavities at the desiredfrequencies. Electromagnetic energy is derived from the cavities bymeans of loop I 9 and concentric transmission line and is supplied to anexternal utilization circuit.

The control of the natural frequencies of the space resonant cavitiesand hence the control of the operating frequency of the device is,obtained by the longitudinal position of the tuning ring I6. As the ringI6 is inserted greater distances into annular groove I5, the operatingfrequency of the device is decreased. This feature of operation may beconsidered as occurring due to the increase of the capacitance effect ofthe tuning ring as a greater effective surface thereof is positioned inannular groove I5. .Of course, in a system of this nature wherein bothmagnetic and electric fields are present, the net effect of such atuning ring cannot properly be described as being solely electric orsolely magnetic. However,

l I have found that effective linear control of the operating frequencyof the device is obtained by positioning the ring l6 longitudinally, andthat the frequency decreases as the ring [6 is inserted greaterdistances in groove I6 and is increased as it is moved out of thegroove.

Another modification of my invention is shown in Fig. 3 which is apartial cross sectional view of an electric discharge device built inaccordance with my invention and many of the elements therein correspondto elements shown in Fig. 1, corresponding elements being assigned likereference numerals. In this modificationof my invention, I provide aplurality of dielectric tuning members, only two of which, 51 and 58,are shown in Fig. 3, and which are preferably constructed of a low lossdielectric material such as quartz. These tuning members are spacedannularly or circumferentially and extend into the cylindrical openings6-l3 of the space resonant cavities. Transverse rod 50 supports anannular member or ring 59 provided with circumferentially spacedapertures 60 adapted to receive restricted ends of the dielectric tuningmembers. A better understanding of the arrangement of the dielectrictuning members may be obtained by referring to Fig. 4 which is a planview showing the associated anode structure, ring 59 and the manner inwhich the tuning members are held in position on the ring.

A preferable form of the tuning members is illustrated in Fig. 5 whereineach member is shown as being provided with a shoulder 6| which servesto seat the member on the upper surface of ring 59, and the restrictedor necked portion of the tuning member is provided with an annularrecess 62 which is adapted to receive retaining and supporting meanssuch as a spring clip 63 attached to ring 59. The spring clip meansmaybe arranged as shown in Fig. 5 wherein a single ring serves to engage apair of adjacent dielectric tuning members and a plurality of suchspring means may be employed as shown in Fig. 4.

By virtue of the tapered relationship of the dielectric tuning stubs ormembers and the resilient character of the spring clip means 52, themembers may be readily inserted through the apertures 60 and will uponinsertion deflect the spring means 63 sufi'iciently to permit the properseating of the tunin members on the upper surface of the ring 59,whereupon the ends of spring means 63 will enter the annular recesses62.

I have found that one of the important advantages of magnetrons built inaccordance with my invention is the substantially linear frequencychange withrespect to the position of the tuning elements or thedistances the tuning elements are moved; Furthermore, I have found thatthe tuning or frequency control is highly effective on completelycoupled or strapped anode structures. The tuning or frequency control ofultra high frequency magnetrons built in accordance with my invention isnot critical; that is, a reasonable amount of mechanical motion producesa useful frequency change. Lastly, the above described types offrequency control are readily applicable to'those arrangements where itis desired to provide, externally accessible means for controlling thefrequency determining means.

While I have shown and described my invention as applied to'an electricdischarge device of the ultra high frequency type embodying variouselements of particular configuration, it will be obvious to thoseskilled in the art that changes and modifications may be made withoutdepart-- ing from myinvention, and I, therefore, aim in the appendedclaims to cover all such changes and modifications as fall within thetrue spirit and scope of my invention.

What I claim asnew and desire to secure by Letters Patent of the UnitedStates is:

1. An ultra high frequency electric discharge device of the magnetrontype comprising a plurality of cooperating electrodes-including acathode and an'annular anode structure having a central opening throughwhich'said cathode extends and providing a plurality of cavityresonators, a pair of magnetic pole pieces longitudinally displaced fromsaid anode structure and each having therein a longitudinal channel,means mounted in the channel of one pole piece supporting said cathodeand constituting a heating current lead, an adjustable tuning memberextending into said anode structure, means defining a transverse slot inthe pole face of the other pole piece, a transverse rod supporting saidtuning member and positioned in the transverse slot in the face of saidother pole piece, and means supporting said transverse rod and saidtuning member comprising a longitudinal rod located within the channelof said other pole piece.

2. An ultra high frequency electric discharge device of the magnetrontype comprising a plurality of cooperating electrodes including acathode and an annular anode structure having a central opening throughwhich said cathode extends and providing a plurality of cavityresonators, a pair of magnetic pole pieces longitudinally displaced fromsaid anode structure and each having therein a longitudinal channel,means mounted in the channel of one pole piece supporting saidcathodeand constituting a heating current lead, an adjustable tuningmember extending into saidanode structure, means defining; a transverseslot in the pole face of the other pole piece, means supporting saidtuning member comprising a rod located in the slot of the other polepiece, and externally accessible control means positioning said rod andsaid member.

3. An ultra high frequency electric discharge device of the magnetrontype comprising a plurality of cooperating electrodes including a cath-4 ode and an annular anode structure having a central opening throughwhich said cathode extends providing a plurality of cavity resonators. apair of magnetic pole pieces longitudinally displaced from said anodestructure and each havin therein a longitudinal channel, means mountedin the channel of one pole piece supporting said cathode andconstituting a heating current lead, means for controlling operatingfrequency of said device comprising a plurality of dielectric tuningmembers which extend into each of said cavity resonators, a membersupporting and positioning said dielectric tuning members, meansadjustably supporting and positioning said member and said tuningmembers comprising a longitudinal rod in the channel of the other polepiece, and externally accessible actuating means controlling theposition of said rod.

4. An electric discharge device of the magnetron type including aplurality of cooperating electrodes including an anode structure havinga plurality of circumferentially spaced anode sections extendingradially inwardly and terminating short of the center of said structureand defining a central opening in said structure, said sections alsodefining between said sections a plurality of circumferentially disposedcavity resonators communicating with said opening, a generally annularchannel having substantially depth formed in said anode structure nearthe inner ends of said sections, a cylindrical tuning member havingsubstantial length extending a variable distance lengthwise into saidchannel whereby a substantially variable portion of the surface of saidtuning member is juxtaposed to a corresponding portion of the surface ofsaid channel, and means attached to said tuning member for moving saidtuning member variable distances into said channel whereby the tuningeffect of said tuning member may be varied in generally linear relationto the distance which said member extends into said channel.

RALPH J. BONDLEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,288,812 Linder July '7, 19422,233,482 Linder Mar. 4, 1941 2,167,201 Dallenbach July 25, 19392,115,521 Fritz, et al Apr. 26, 1938 2,163,589 Dallenbach June 27, 19392,163,147 Samuel June 20, 1939 2,348,986 Linder May 16, 1944 2,408,234Spencer Sept. 24, 1946 2,408,235 Spencer Sept. 24, 1946 2,408,355 TurnerSept. 24, 1946 FOREIGN PATENTS Number Country Date 509,102 Great BritainJuly 11, 1939 215,600 Switzerland Oct. 16, 1941

